Computer pointing device

ABSTRACT

A case top for the housing of a mouse-type computer pointing device is made of a single piece of plastic. The case top includes securing arms which engage securing hooks extending from a case bottom of the housing, allowing the case top to be releasably fastened to the case bottom with a single screw. The case top includes two user actuable buttons attached to a main body by two spring arms, all formed as a single one-piece case top. The two buttons actuate an integrated switch package having two momentary switches within the package. The integrated switch package consists of two pieces: a switch case and a switch spring. The switch package is mounted on a printed circuit board. The switch case engages the case bottom to help secure both the switch package and the printed circuit board. User actuation of the switch package causes the switch spring to flex and make momentary electrical contact with contacts on the printed circuit board. The pointing device includes a cord strain relief unit that is held solely by the case bottom. The pointing device also includes a ball retaining cage that is removably securable to the bottom side of the housing while the case top and case bottom are secured together.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.08/367,938, filed Jan. 3, 1995, now U.S. Pat. No. 5,828,364.

TECHNICAL FIELD

This invention relates generally to computer pointing devices and, moreparticularly, to ball-type pointing devices.

BACKGROUND OF THE INVENTION

In many of today's computers, commands are entered into the computer byusing a mouse pointing device. Typically, the mouse includes a housingpartially enclosing a rotatable ball and one or more depressablebuttons. As the mouse is moved along a surface, oftentimes a table top,transducers within the mouse sense the ball's rotation and generatesignals output to the computer. The signals control a correspondingmovement of a cursor, or pointer, on a visual display of the computer.Depending upon the location of the cursor on the visual display, avariety of commands can be entered into the computer by depressing thebuttons and actuating switches positioned within the housing. Examplesof such commands include launching an application program, pulling downa menu, opening a document, selecting a portion of a document forediting, and creating terminal or other points in a graphic pattern onthe visual display.

Today's commercially available mice are assembled from a relativelylarge number of pieces. Generally, the greater the number of parts in amouse the more expensive it is to produce. This is because both thenumber of manufacturing and assembly steps increase with the increasingnumber of parts. For example, most of today's mice have an upperhousing, or case top, assembled from at least two pieces, with thebuttons being formed from a separate piece that must be attached to therest of the case top. While one-piece case top mice are currentlyavailable on the market, they require additional pieces within thehousing to accommodate the one-piece case top design, and so there is nooverall parts reduction. Also, the currently available one-piece piececase top mice have an unsatisfactory limitation on button movement.Currently available mice have the upper and lower parts of the housingfastened together by two or more screws. Currently available mice haveswitches assembled from a number of separate pieces. Currently availablemice have a multi-piece means of biasing the ball against transducers.

Overall, it is desirable to design a mouse pointing device that can bemanufactured from as few pieces and in as few manufacturing and assemblysteps as possible, without sacrificing the requisite operatingcharacteristics and durability.

SUMMARY OF THE INVENTION

According to the principles of the present invention, a computer inputdevice includes a housing formed from a case bottom and a case top. Thecase top is of unitary construction and includes a main body and a firstbutton movable between rest and actuation positions for user actuationof a first switch. A first spring arm, extending from the main body toapproximately a middle portion of the first button, biases the firstbutton into the rest position. A first guide track protruding from thecase bottom receives a first restraining arm extending from the firstbutton and restricts the lateral, torsional and upward movement of thefirst restraining arm and the first button attached thereto. Preferably,the case top of the input device of the present invention includes asecond button movable between rest and actuation positions, a secondspring arm extending from the main body to the second button and biasingthe second button into the rest position, and a second restraining armextending from the second button and received by a second guide trackprotruding from the case bottom. The case top further includes securingarms which engage securing hooks projecting from the case bottom,allowing the case top to be releasably fastened to the case bottom witha single selectively removable fastener.

The computer input device of the present invention further includes aswitch package consisting of a switch case of unitary construction and aswitch spring of unitary construction. The switch spring is positionedwithin a recess of the switch case, and the switch package is mounted ona printed circuit board positioned within the housing of the inputdevice. The case top includes first and second actuating membersrespectively projecting from the first and second buttons and. Upon useractuation of the first and second buttons, the first and secondactuating members respectively contact and flex the switch spring tomake first and second electrical connections between the switch springand first and second contacts on the circuit board. The switch caseengages the case bottom of the housing, securing the switch package tothe case bottom and helping to secure the printed circuit board withinthe housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a mouse pointing device of the present invention on a tabletop connected to a computer having a visual display.

FIG. 2 is an enlarged bottom perspective of the mouse pointing device ofFIG. 1.

FIG. 3 is an exploded top perspective view of the mouse pointing deviceof FIG. 1.

FIG. 4 is an exploded bottom perspective view of the mouse pointingdevice of FIG. 1.

FIG. 5 is an enlarged bottom perspective view of the mouse pointingdevice of FIG. 1 showing the interior of the case top.

FIG. 6 is an enlarged top perspective view of the mouse pointing deviceof FIG. 1 showing the interior of the case bottom.

FIG. 7 is an enlarged top plan view of the case bottom of the mousepointing device of FIG. 1 showing a spring rod and roller unit in place.

FIG. 8 is a cross-sectional view showing a closed mold duringmanufacture of the case top.

FIG. 9 is a cross-sectional view showing the mold of FIG. 8 open priorto ejection of the molded case top.

FIG. 10 is a cross-sectional view showing the molded case top ejectedfrom the lower half of the mold of FIG. 9.

FIG. 11 is an enlarged rear perspective view showing the switch caseused in the mouse pointing device of FIG. 1.

FIG. 12 is a front perspective view showing the switch case of FIG. 11.

FIG. 13 is an enlarged, bottom perspective view showing the interior ofthe switch case of FIG. 11 with the switch spring in place.

FIG. 14 is a reduced scale perspective view showing the switch spring ofFIG. 13.

FIG. 15 is an enlarged, elevational, cross-sectional view showing theswitch case of FIG. 11 mounted on the printed circuit board, with theswitch spring positioned within the switch case in the restconfiguration.

FIG. 15A is an enlarged fragmentary view of a circled portion of theswitch case of FIG. 15 shown mounted on a printed circuit board ofgreater thickness than depicted in FIG. 15.

FIG. 16 is an elevational, cross-sectional view of the mounted switchcase of FIG. 15 showing case top actuating members, and showing onecontact leaf in an actuation position and another contact leaf in a restposition.

FIG. 17 is a rear perspective view of the switch case of FIG. 11 shownstacked on another switch case.

FIG. 18 is an enlarged perspective view of a ball retaining cage used inthe mouse pointing device of FIG. 1.

FIG. 19 is an elevational view of the ball retaining cage of FIG. 18.

FIG. 20 is an enlarged, right side, top perspective view of the casebottom of the mouse pointing device of FIG. 1 showing the assembledcomponents within the interior of the case bottom.

FIG. 21 is a top plan view of the assembled components and case bottomof FIG. 20.

FIG. 22 is an enlarged, right side elevational view of a forward portionof the assembled components and case bottom of FIG. 20.

FIG. 23 is a perspective view of the disassembled spring rod and rollerunit of FIG. 7.

FIG. 24 is an enlarged perspective view of a cord strain reliefcomponent used in the mouse pointing device of FIG. 1.

FIG. 25 is a top plan view of the cord strain relief component of FIG.24.

DETAILED DESCRIPTION

FIG. 1 shows a mouse 100 of the present invention resting on and free tomove along a tabletop horizontal surface 102. The mouse 100 is connectedby a cord 104 to a computer 106 having a visual display 108. Transducers110 (see FIG. 3) within the interior of the mouse 100 translate motionof the mouse along the horizontal surface 102 into a correspondingmotion of a cursor 112 on the visual display 108.

As shown in FIG. 1 and 2, the mouse 100 includes a housing 114 formedfrom a case top 200 and a case bottom 300. Each of the case top 200 andcase bottom 300 is of unitary construction, with each of theirrespective assembly of components described below being molded as anintegral unit. The case top 200 and the case bottom 300 are eachpreferably constructed from ABS plastic. A top sidewall 201 of the casetop 200 defines a top side of the housing 114, and a bottom sidewall 301of the case bottom 300 defines a bottom side of the housing. Left andright sidewalls 240 of the case top 200 and left and right sidewalls 308of the case bottom 300 together respectively defme left and right sidesof the housing 114. A curved rear sidewall 205 of the case top 200,together with a curved rear sidewall 323 of the case bottom 300, definea curved rear side of the housing 114. A front sidewall 232 of the casetop 200 (see FIG. 5) and a front sidewall 322 of the case bottom 300(see FIG. 6) together define a front side of the housing 114. The casetop 200 and case bottom 300 together define an interior compartmentwithin the housing 114.

As shown in FIG. 2, the housing 114 of the mouse 100 partially enclosesa ball 130, which rests in a middle portion of the case bottom 300 andprotrudes through a hole 158 in the bottom side of the housing. As themouse 100 is moved along the horizontal surface 102 of FIG. 1, thehorizontal surface contacts and rotates the ball 130. Transducers 110(see FIG. 3) within the interior compartment of the mouse 100 translatethe rotation of the ball 130 into movement of the cursor 112 on thevisual display 108 of the computer 106.

The main components of the mouse 100 are shown in FIGS. 3 and 4. Aretaining cage 150 receives the ball 130 therewithin and is removablysecured to the case bottom 300. The retaining cage 150 allows the ball130 to rotate freely while protecting the components within the mouse100 from the ball in the event the mouse is dropped or moved suddenly.For a more detailed description of the retaining cage 150 and itssecurement to the case bottom 300, see FIGS. 6, 18 and 19, and thediscussion below.

A biasing spring unit 600, consisting of a selectively bent spring rodor wire spring 602 and a roller 604, is positioned within the interiorof the housing 114 of the mouse 100. The wire spring 602 is preferablyconstructed from a small diameter stainless steel rod, and the roller604 is preferably constructed from Acetal. The case bottom 300 securesor supports each end portion of the wire spring 602, and the roller 604is rotatably disposed on one end portion of the wire spring. The roller604 rotatably contacts the ball 130, and is biased against the ball bythe wire spring 602, for coupling the ball to the transducers 110. For amore detailed description of the biasing spring unit 600, itspositioning within the interior of the housing 114 and its functioningto couple the ball 130 to the transducers 110, see FIGS. 7, 20, 21 and23, and the discussion below.

As shown in FIG. 3, a printed circuit board 500 is positioned within thehousing 114 of the mouse 100. Mounted on the printed circuit board 500are two transducers 110, each including a paired light-emitting elementor diode (“LED”) 502 and light-detecting element or photodetector 504. Anotched encoder wheel 506 is positioned between each paired LED 502 andphotodetector 504. Each encoder wheel 506 is axially mounted on anencoder shaft 510 which is rotatably supported by a wheel support arm302 and a shaft support arm 304 which extend upwardly from the interiorside of the bottom sidewall 301 of the case bottom 300. The biasingspring unit 600 biases the ball 130 against both of the encoder shafts510, and as the ball rotates, the shafts turn accordingly (see FIG. 21).Notches 508 on the rotating encoder wheels 506 sweep by the LEDs 502,selectively modulating the light received by the photodetectors 504which output signals in response thereto.

Control circuitry 512 on the printed circuit board 500 processes thesignals output by the photodetectors 504 and then sends to the computer106 (see FIG. 1), via the cord 104, signals controlling the directionand distance of cursor 112 movement on the visual display 108. Thecircuitry 512 is connected by a coupler 514 to the cord 104. A strainrelief unit 700 grasps the cord 104 and is secured to the case bottom300 to assure that mechanical strain on the cord is transmitted to thecase bottom and not to the coupler 514. For a more detailed descriptionof the strain relief unit 700 and its securement to the case bottom, seeFIGS. 20, 24 and 25, and the discussion below.

A switch package 400, consisting of only a switch case 402 having aninterior recess 404 and a switch spring 470 positioned within theinterior recess of the switch case, is mounted on top of the printedcircuit board 500. Each of the switch case 402 and switch spring 470 isof unitary construction, with each of their respective assembly ofcomponents described below being formed as an integral unit. The switchcase 402 is preferably constructed from polycarbonate, and the switchspring 470 is preferably constructed from beryllium-copper. The switchcase 402 includes two photoelectric housing units 430 which position andalign the transducers 110, as well as cover them for protection fromambient light and dust.

As shown in greater detail in FIGS. 13 and 15 and as described infurther detail below, the interior recess 404 has an opening at thebottom of the switch case 402 so that the switch spring 470 positionedtherein can engage the printed circuit board 500. Left and right contactleaves 472 of the switch spring 470 selectively and momentarily makeelectrical contact with left and right contacts 520 mounted on theprinted circuit board. The contacts 520 are positioned below the contactleaves 472 and connected to the circuitry 512 on the printed circuitboard 500. The contacts 520 are also held in place by an arm 416extending from within the recess 404 of the switch case 402.

The shape of the left and right portions of the switch spring 470 issubstantially symmetrical. As shown in greater detail in FIGS. 13-16 andas described in further detail below, the switch spring 470 includesleft and right C-shaped leaf spring elements 476 that, in the restposition of the switch spring, bias the contact leaves 472 away from thecontacts 520 on the printed circuit board 500. The switch spring 470further includes a common contact ribbon 474 which is fixedly andelectrically connected to the printed circuit board 500.

As shown in FIGS. 1 and 3, the case top 200 includes a main body 202,and side-by-side primary and secondary buttons 204 and 206,respectively, positioned forward of the main body. The primary andsecondary buttons 204 and 206 are generally rectangular in shape andtogether with the main body 202 defme the top side of the housing 114 ofthe mouse 100. The buttons 204 and 206 are movable between rest andactuation positions and, as best shown in FIGS. 4 and 5, each includesan actuating member 208 attached thereto and extending downward into theinterior of the mouse 100. Actuator slots 420 (see FIG. 3) in the topside of the switch case 402 receive the actuating members 208, and thefree ends of the actuating members touch the contact leaves 472 of theswitch spring 470. Depressing one or both of the buttons 204 and 206into the actuation position flexes the corresponding contact leaf 472downwards, making its electrical contact with the corresponding contact520 on the printed circuit board 500 (see FIG. 16). This produces aswitch signal transmitted to and processed by the circuitry 512 on theprinted circuit board 500 (see FIG. 3) and output to the computer 106(see FIG. 1) for entering commands into the computer.

Upon release of the buttons 204 and 206, spring arms 210 (see FIGS. 4and 5), each connecting the main body 202 to one of the buttons 204 and206, bias the buttons upward away from the actuation position into therest position. The C-shaped leaf spring elements 476 of the switchspring 470 return the contact leaves 472 of the switch spring to therest position, out of contact with the contacts 520 on the printedcircuit board 500 (see FIG. 15).

As best shown in FIG. 5, each of the spring arms 210, connecting one ofthe primary and secondary buttons 204 and 206 to the main body 202 ofthe case top 200, includes a main body support member or leg 220 thatextends downward from the interior side of the main body 202, and abutton support member or leg 222 that extends downward from the interiorside of a respective one of the buttons 204 and 206. Each spring arm 210also includes a rectangular leaf spring 224 oriented approximatelyparallel to the top sidewall 201 of the case top 200 and extendingbetween a free end of the main body leg 220 and a free end of the buttonleg 222.

The main body legs 220 are each connected to the main body 202 at aposition rearward of a forward edge of the main body 202. The buttonlegs 222 are each connected to a corresponding one of the buttons 204and 206 at a position forward of a rearward edge of the correspondingbutton and proximate to a middle portion of the button. The spring arms210 allow each of the primary and secondary buttons 204 and 206 tomaintain a substantially horizontal attitude when depressed. Thiscontrasts favorably with other attempts at unitary case top design,where the buttons are attached to the main body along adjacent edges andpivot about these edges. In the case of such an attachment, known to theart as a “living hinge”, portions of the button distal from the mainbody experience greater displacements than portions proximate to themain body, resulting in an unsatisfactory tilting button movement.

Also shown in FIG. 5, a restraining member or arm 230 extends downwardfrom the interior side of each of the primary and secondary buttons 204and 206. The restraining arms 230 are each connected to a correspondingone of the buttons 204 and 206 at a forward edge of the correspondingbutton and to the interior side of the front sidewall 232. Tabs 234project forward from the free ends of the restraining arms 230.

As shown in FIG. 7, the case bottom 300 includes two restraining membersthat are vertically oriented tracks 320, each designed to receive one ofthe restraining arms 230 of the buttons 204 and 206. Each of the guidetracks 320 is formed by a parallel plate structure 324, including asecuring plate 326 and a parallel support plate 328. As shown in FIG. 6,the plates 326 and 328 are both connected to the interior sides of thefront and bottom sidewalls 322 and 301 of the case bottom 300, andoriented approximately parallel to the left and right sidewalls 308 ofthe case bottom. Located within each guide track 320 is a horizontalshelf 330 spanning the gap between the corresponding securing plate 326and supporting plate 328 and connected to the sides of the plates facingone another. The shelf 330 extends inward from the interior side of thefront sidewall 322 of the case bottom 300.

When the case top 200 is attached to the case bottom 300, each of thevertical guide tracks 320 of the case bottom slideably receives acorresponding one of the restraining arms 230 of the primary andsecondary buttons 204 and 206. The tab 234 extending from therestraining arm 230 projects forward and beneath the horizontal shelf330 in the guide track 320. In the rest position of the buttons 204 and206, each of the forward projecting tabs 234 contacts the underside ofthe corresponding shelf 330, and thereby limits the upward travel of thebuttons resulting from the upward bias force imparted by the spring arms210 to the buttons.

The guide tracks 320 of the case bottom 300 also maintain the lateralseparation of the primary and secondary buttons 204 and 206 and limitany torsional tilting movement of the buttons. The restraining arms 230,each extending from the interior side of one of the buttons 204 and 206of the case top 200, are restrained by the parallel plate structures 324against any substantial leftward or rightward horizontal movement.

Referring again to FIG. 5, a supplementary restraining arm 236 isprovided for the primary button 204 and extends downward from theinterior side of the primary button. As shown in FIG. 7, a supplementaryguide track 332 is formed by a groove 334 (see also FIG. 6) in theinterior side of the front sidewall 322 of the case bottom 300. Thesupplementary restraining arm 236 includes a forwardly projecting tab234, and an undercut 333 is located within the groove 334 forming thesupplementary guide track 332. The supplementary track 332 receives thesupplementary restraining arm 236, and the tab 234 projecting from thesupplementary restraining arm engages the undercut 333 located withinthe groove 334 in a manner similar to and for the same purpose asdescribed above.

The case top 200 has left and right securing members or arms 212, asshown in FIGS. 4 and 5, extending downward from the interior side of themain body 202 of the case top, which engage left and right securingmembers or hooks 306, shown in FIGS. 3 and 6, projecting laterallyinward from the interior side of the left and right sidewalls 308 of thecase bottom 300 for purposes of releasably attaching the case top 200 tothe case bottom 300. A tab 242 extends forward from the free end of eachof the left and right securing arms 212 (see FIG. 5). Each of the leftand right securing hooks 306 releasably engages a corresponding one ofthe securing tabs 242 extending from the respective one of the securingarms 212 to removably and securedly hold the case bottom 300 and thecase top 200 together.

As shown in FIGS. 4 and 5, a top fastening member 214 extends downwardfrom the interior side of the main body 202 and includes a cylindricalshaft 216 having a bore 218. As shown in FIGS. 3 and 6, a bottomfastening member 312 extends upwardly from the interior side of thebottom sidewall 301 of the case bottom 200. The bottom fastening member312 has a cylindrical recess 316 which receives the cylindrical shaft216 of the case top fastening arm 214. A selectively removable fasteneror self-tapping screw 310, coaxially received by a bore 314 in thebottom fastening arm 312 of the case bottom 300 and the bore 218 in thetop fastening member 214 (see FIG. 5) of the case top 200, releasablyfastens the case bottom to the case top using only a single screw.

As shown in FIG. 5, the left and right securing arms 212 are locatedproximate to the left and right sidewalls 240, respectively, of the casetop, and are each connected to the interior side of the main body and toa rearward facing side of a corresponding one of the main body legs 220of the spring arms 210. Indeed the corresponding securing arm and springarm can be considered parts of a single structure. This leads toimportant economies when manufacturing the case top 200. FIGS. 8-10 showcross-sectional views of a mold 750 having two lift-cores 752 used toform the case top 200, showing the cross-section taken just forward ofthe main body leg 220 and securing arm 212 as indicated by the line 8—8in FIG. 5. FIG. 8 shows the mold 750 in the closed position, while FIG.9 shows the mold open prior to ejecting the molded case top 200. Asingle one of the lift-cores 752 simultaneously forms the rectangularleaf spring 224 of one of the spring arms 210 and the securing tab 242of the adjacent securing arm 212. As shown in FIG. 10, the lift-cores752 eject the case top 200 from the mold 750 and simultaneously releasethe rectangular leaf springs 224 and securing tabs 242. A thirdlift-core (not shown) is used to form each of the projecting tabs 234extending from the corresponding one of the restraining andsupplementary restraining arms 230 and 236 of the primary button 204,and a fourth lift-core (not shown) is used to form the projecting tab234 extending from the restraining arm 236 of the secondary button 206.Thus, only four lift-cores are required to mold the unitary case top 200of the present invention.

As shown in FIGS. 11-13, the switch case 402 has a top sidewall 406,front and rear sidewalls 408 and 410, respectively, and left and rightsidewalls 412 and 414, respectively. The switch case 402 has no bottomsidewall. As shown in FIG. 21, the switch package 400 is mounted on aforward portion 540 of a top side of the printed circuit board 500. Asshown in FIG. 13, a rear snap mounting leg 422 extends downward from alower edge of the rear sidewall 410 of the switch case 402. A tab 426extends horizontally rearward from the free end of the rear mounting leg422. A snap mounting leg 424 extends downward from the lower edge ofeach of the left and right sidewalls 412 and 414 of the switch case 402.A tab 426 extends laterally outward from the mounting leg 424. Mountingslots 530 in the printed circuit board 500 (see FIG. 4) each receive oneof corresponding snap mounting members or legs 422 and 424. Alignmentpins 418 (see FIGS. 4, 13 and 15) extend downward from the interior sideof the top sidewall 406 of the switch case 402 and are received byalignment holes 532 in the printed circuit board 500, thereby laterallyaligning the switch case relative to the circuit board.

Each of the tabs 426 extends below and contacts the bottom side of theprinted circuit board 500 to firmly secure the switch package 400 to theprinted circuit board, as shown in FIG. 22. Each of the tabs 426 has anupward facing surface 427 with a downwardly directed taper away from thefree end of the corresponding mounting leg 422 and 424, as shown in FIG.15. The mounting slots 530 in the circuit board 500 are sized to allowthe mounting legs 422 and 424 to flex. The tapered upward facing surface427 allows the switch package to be firmly secured to printed circuitboards 500 of varying thicknesses. For example, if the switch case 402is mounted on a slightly thicker than expected circuit board 500, themounting legs 424 would flex laterally inward and the printed circuitboard would contact laterally outward portions of the tapered upwardlyfacing surfaces 427 (see FIG. 15A).

As shown in FIGS. 11 and 13, the photoelectronics housing units 430 ofthe switch case 402 are positioned at and extend rearward of the rearsidewall 410 of the switch case. Each housing unit 430 includes an LEDcover 432 and a photodetector cover 434. Each of the covers 432 and 434has an open bottom and an interior recess which receives a correspondingone of the LEDs 502 and photodetectors 504 mounted on the printedcircuit board 500. As shown in FIG. 13, a lower portion 436 of theinterior surface of each cover 432 and 434 has an inwardly directedtaper away from the printed circuit board 500, and an upper portion 438of the interior surface of each cover is approximately vertical. As thephotoelectronics housing units 430 are placed over the LEDs 502 andphotodetectors 504 upon assembly of the mouse 100 (see FIG. 3), thetapered lower portion 436 of the interior surface of the covers 432 and434 guides the corresponding one of the LEDs and photodetectors receivedtherein into position within the upper portion thereof. The LEDs 502 andphotodetectors 504 are thus positioned and aligned for a subsequentwave-soldering process. This provides a distinct advantage over thecurrent art, which requires either placement and removal of a positionand alignment fixture apparatus or hand alignment after thewave-soldering process.

As shown in FIG. 13, each of the covers 432 and 434 of eachphotoelectronics housing unit 430 has an open side 440 that faces theopen side of the other cover to allow light emitted by the LED 502 inthe cover 432 to be detected by the photodetector 504 in thecorresponding cover 434. A gap 442 (see FIG. 12) is provided between thecovers 432 and 434 of each housing unit 430 to accommodate acorresponding one of the notched encoder wheels 506 (see FIGS. 20 and21) therein. As previously discussed, the encoder wheel 506 selectivelymodulates the light received by the photodetector 504 from thecorresponding LED 502.

As shown in FIGS. 21 and 22, the switch package 400 is mounted adjacentto a forward edge of the printed circuit board 500. Referring to FIG.22, the front sidewall 408 of the switch case 402 extends downward at aposition forward of the front edge of the printed circuit board 500. Acase securing member or ridge 428, located on the lower exterior side ofthe front sidewall 408 of the switch case 402 projects horizontallyforward. A securing member 336 projects horizontally rearward from eachof the securing plates 326 of the parallel plate structures 324 of thecase bottom 300 (see FIG. 6). The printed circuit board 500, togetherwith mounted switch package 400, is positioned within the interior ofthe case bottom 300. The securing ridge 428 of the switch case 402extends forward below and contacts the underside of the securing members336 of the case bottom 300, thereby restricting the upward verticalmovement of the forward portion 540 of the printed circuit board 500(see FIGS. 21 and 22).

As shown in FIGS. 6 and 7, a support 338 extends rearward from each ofthe support plates 328 of the parallel plate structures 324 of the casebottom 300 along the interior side of the bottom sidewall 301 of thecase bottom. The supports 338 contact the underside of the securingridge 428 and support the front sidewall 408 of the switch case 402 (seeFIG. 22). The securing members 336 and the supports 338 of the casebottom 300 together function as a bottom securing member to releasablyengage the securing ridge 428 and removably secure to the case bottomthe switch package 400 and the circuit board 500 attached thereto. Withthe upward and downward movement of the switch case 402 respectivelyrestricted by the securing members 336 and the supports 338 of the casebottom 300, the switch package has a determined vertical position withinthe housing 114 of the mouse 100 independent of any variance inthickness of the printed circuit board 500. This determined verticalposition is important since actuation of the switch package 400 iseffected by vertically depressing the primary and secondary buttons 204and 206 of the case top 200, and any appreciable variance in verticalpositioning of the switch package 400 relative to the buttons mightaffect its proper functioning.

As shown in FIGS. 6 and 7, left and right block supports 340 extendupward from the interior side of the bottom sidewall 301 of the casebottom 300. The block supports 340, together with the supports 338,support the forward portion 540 of the printed circuit board 500 thereonand restrict its downward movement (see FIG. 22).

The printed circuit board 500 has left and right holes 534 (see FIG. 4),and the switch case 402 has left and right alignment holes 444, locatedon the lower edge of the rear sidewall 410 of the switch case (see FIG.13), positioned above the alignment holes in the printed circuit board.The corresponding holes 534 of the printed circuit board 500 andalignment holes 444 of the switch case 402 receive left and rightalignment pins 342 therethrough which extend upward from the interiorside of the bottom sidewall 301 of the case bottom 300 (see FIG. 6). Thealignment pins 342 restrict the lateral movement of the switch package400 and the printed circuit board 500 attached thereto. The free ends ofthe pins 342 also defme a seating surface for the switch case 402,thereby fixing the vertical position of the switch package 400 relativeto the case bottom 300. Left and right bracket supports 344, extendingupward from the interior side of the bottom sidewall 301 and from theinterior sides of left and right sidewalls 308 of the case bottom 300(see FIG. 6), support a rear portion 542 of the printed circuit board500 thereon and restrict its left and right lateral movement (see FIG.21).

As shown in FIGS. 4 and 5, a hold-down member or arm 250 extendsdownward from the interior side of the main body 202 of the case top200. The hold-down arm 250 engages the top side of the rear portion 542of the printed circuit board 500, when the mouse 100 is assembled.Together with the bracket supports 344, supports 338 and block supports340 of the case bottom 300, and the interaction of the case bottomsecuring members 336 with the securing ridge 428 of the mounted switchcase 402, the hold-down arm 250 securely holds the printed circuit board500 in position within the housing 114 of the mouse 100.

FIG. 13 shows the switch spring 470 positioned within the interiorrecess 404 of the switch case 402, and FIG. 14 shows the switch springremoved from the switch case. Each of the left and right contact leaves472 has a pair of holding holes 480 located in a laterally outward endthereof which each receive a holding pin 446. The holding pins 446extend downward from a lower edge of the left and right sidewalls 412and 414 of the switch case 402. Subsequent to being received by theholding holes 480 upon assembly of the mouse 100, the holding pins 446are either heat staked or cold staked, thereby fixing the laterallyoutward end of each of the left and right contact leaves 472 to theswitch case 402.

As shown in FIGS. 13, 15 and 16, each of the left and right contactleaves 472 of the switch spring 470 is oriented generally parallel tothe printed circuit board 500 and extends from its fixed end in adirection towards the center of the switch case 402 and terminates in afree end. As shown in FIGS. 13 and 14, the left and right C-shapedspring elements 476 are each disposed in an opening 478 in thecorresponding one of the left and right contact leaves 472 adjacent toits free end. The C-shaped spring element 476 is connected to andextends from a position proximate to the free end of the correspondingcontact leaf 472 in a direction back towards the fixed end of thecorresponding contact leaf and terminates in a free end. In an unflexedstate the C-shaped spring elements 476 each pass through the opening 478in the corresponding one of the contact leaves 472, and the free ends ofthe spring elements reside at positions displaced from a plane definedby the contact leaves. When positioned within the recess 404 of theswitch case 402, the C-shaped spring elements 476 curve upward with amid-portion toward the interior side of the top sidewall 406 of theswitch case. The free end of each of the C-shaped spring elements 476 isbent back on itself to make a horizontal end portion 482 and to leave aportion 479 of the opening 478 in each of the contact leaves 472unobstructed to receive a corresponding one of left and right supportarms 448 therethrough (see FIGS. 13, 15 and 16).

As shown in FIGS. 13, 15 and 16, the left and right support members orarms 448 extend downward from the interior side of the top sidewall 406of the switch case 402 and are preferably molded as part of the samestructures that include the alignment pins 418, discussed above. Each ofthe support arms 448 extends into the unobstructed portion 479 of acorresponding one of the openings 478 in the left and right contactleaves 472 of the switch spring 470 (see FIG. 14). Each has a laterallyextending tab 450 at a free end thereof projecting toward the center ofthe switch case 402. Each of the end portions 482 of the respectiveC-shaped spring elements 476 of the switch spring 470 is supported by acorresponding one of the tabs 450. The left and right support arms 448are spaced apart so that when the switch spring 470 is mounted withinthe recess 404 of the switch case 402, the C-shaped spring elements 476are held by the support arms in a somewhat flexed state with a smallerradius of curvature than when in the unflexed state. Thus, the endportions 482 of each C-shaped spring element 476 flexingly engage thecorresponding one of the tabs 450 and a center facing side of thecorresponding support arm 448. With this arrangement, each of theC-shaped spring elements 476 biases the free end of the correspondingone of the contact leaves 472 upwards away from the printed circuitboard 500. As shown in FIGS. 15 and 16, restraining members or ridges452 extend downward from the interior side of the top sidewall 406 ofthe switch case 402 and engage a corresponding one of the upwardlybiased free ends of the contact leaves 472 to limit the upward movementthereof resulting from the bias force imparted to each of the contactleaves by the respective one of the C-shaped spring elements 476.

As shown in FIGS. 13 and 14, the common contact ribbon 474 of the switchspring 470 connects together each of the fixed ends of the left andright contact leaves 472. When the switch spring is positioned withinthe recess 404 of the switch case 402, the common contact ribbon 474 isdisposed approximately parallel and adjacent to the interior side of therear sidewall 410 of the switch case. A common contact strip 484 extendsfrom a middle portion of the common contact ribbon 474. A common contactarm 454 extends downward from the interior side of the top sidewall 406of the switch case 402. The common contact strip 484 is aligned with thecommon contact arm 454, and a free end portion of the common contactstrip wraps around a free end of the common contact arm. When the switchpackage 400 is mounted on the circuit board 500, the common contact arm454, along with the common contact strip 484, is embedded into theprinted circuit board, where wave soldering fixedly and electricallyconnects the common contact strip 484 to an electrical common contact ofthe circuitry 512 on the printed circuit board.

As previously noted, each of the actuating members 208 extends downwardfrom the interior side of one of the primary and secondary buttons 204and 206 of the case top 200 (see FIG. 5). Each actuating member 208passes through a corresponding one of the actuator slots 420 formed inthe top sidewall 406 of the switch case 402 (see FIG. 11). Each of thecontact leaves 472 of the switch spring 470 has a cross piece 486 (seeFIGS. 13 and 14) which is engaged by the free end of the correspondingactuating member 208. As shown in FIG. 16, depressing one of the buttons204 and 206 downward from the rest position to the actuation positioncauses the respective actuating member 208 to press downward on thecorresponding one of the cross pieces 486. This overcomes the upwardbias imparted to the contact leaf 472 by the corresponding one of theC-shaped spring elements 476, and the contact leaf flexes downward andmakes contact with a corresponding one of the electrical contacts 520connected to the circuitry 512 on the printed circuit board 500. Thedownward movement of the actuating members 208 is limited by stops 209which extend laterally from the actuating members (see FIG. 5) and, uponuser depression of one or both of the buttons 204 and 206, contact theexterior side of the top sidewall 406 of the switch case 402 (see FIG.16).

FIG. 17 shows one switch case 402A stacked on another switch case 402B.The stackability of switch cases leads to certain economies. Switchcases can be manufactured in one location, and packed in a nested stackfor safe shipping to a mouse assembly site in another location. Withoutthe stacking feature, each individual switch case would have to bewrapped to assure against damage during transit from the switch casemanufacture site to the mouse assembly site.

As seen in FIG. 11, a rear notch 460 is formed on the exterior of theswitch case 402 at the junction of the top and rear sidewalls 406 and410 and positioned to be directly below the rear mounting leg 422extending downward from the rear sidewall of a switch case stackedthereabove. Similarly, left and right side notches 462 are formed on theexterior of the switch case 402 at the junctions of the left and rightsidewalls 412 and 414 with the top sidewall 406, respectively, andpositioned to be directly below the left and right side mounting legs424, respectively, extending downward from the left and right sidewallsof the switch case stacked thereabove (see FIGS. 11 and 12). In suchfashion, the rear notch 460 on the lower switch case 402B in the stackreceives the rear mounting leg 422 of the upper switch case 402A stackedon top, while the side notches 462 of the lower switch case accommodatethe side mounting legs 424 of the upper switch case (see FIG. 17). Slots464 (see FIG. 11), located in the top sidewall 406 of the switch case402B (see FIG. 17), receive the alignment pins 418 (see FIG. 13) of theupper switch case 402A (see FIG. 17) stacked on top, thereby restrictingrelative lateral movement of the stacked switch cases. Additionally,each switch case 402 has stacking posts 468 located on the top frontleft and right comers of the switch case (see FIG. 11). As shown in FIG.17, the stacking posts 468 on the lower switch case 402B contact thelower edge of the front sidewall 408 of the upper switch case 402Astacked on top. The outer edges of the photodetector covers 434 of thehousing units 430 are tapered so that a top portion of the photodetectorcover of the lower switch case 402B nests within an open bottom portionof the photodetector cover of the upper switch case 402A stacked on top.

As shown in FIGS. 18 and 19, the ball retaining cage 150 generallyincludes an annular baseplate 152, a curved shield 154, and projectingwings 156. The curved shield 154 extends upward from the top side of theannular baseplate 152 into the interior compartment of the housing 114of the mouse 100 (see FIG. 20). The curved shield 154 is generallyspherical in curvature and is connected to the top side of the annularbaseplate 152 at two generally diametrically opposite portions of thetop side of the baseplate. The ball 130 is rotatably received within theretaining cage 150 and protrudes through the hole 158 in the annularbaseplate 152 which forms a removable part of the bottom sidewall 301 ofthe case bottom 300 (see FIGS. 2 and 3). The curved shield 154 has afirst side opening 160 that is large enough for the passage of the ball130 therethrough upon assembly of the mouse 100 and allows the ball tocontact the encoder shafts 510 (see FIG. 21). The curved shield 154 alsohas a second side opening 162 that allows the roller 604 of the biasingspring unit 600 to contact and bias the ball 130 against the encodershafts 510 (see FIGS. 20 and 21). The wings 156 project horizontallyfrom the curved shield 154 on diametrically opposite sides thereof at aposition spaced above the annular baseplate 152 to form a gap 164between each of the wings and the annular baseplate.

As shown in FIGS. 3, 4 and 6, an approximately circular opening 350 inthe bottom sidewall 301 of the case bottom 300 receives the curvedshield 154 of the retaining cage 150 with the enclosed ball 130.Referring to FIG. 6, the opening 350 has a sidewall 352. The openingincludes approximately diametrically opposite notches 354 which receivethe wings 156 upon initial placement of the retaining cage 150 in theopening 350. Subsequent rotation of the retaining cage 150 causes thegaps 164 formed between the wings 156 and annular baseplate 152 toreceive horizontal shelves 356 located in the sidewall 352 of the casebottom opening 350 proximate to the notches 354. The projecting wings156 rest on the top side of the horizontal shelves 356, while theannular baseplate 152 contacts the bottom side of the shelves, therebyremovably securing the retaining cage 150, and ball 130 enclosedtherein, to the case bottom 300.

FIGS. 7, 20 and 23 show the biasing spring unit 600 used for couplingthe ball 130 to the transducers 110. The wire spring 602 has four bendsor turns defining five sections. The end section 606 of the wire spring602 is held by an attaching arm 370 connected to and extending upwardsfrom the interior side of the bottom sidewall 301 of the case bottom300. The end section 606 of the wire spring is oriented horizontally andapproximately parallel to the front sidewall 322 of the case bottom 300.The rear facing side of the right block 340, which extends upward fromthe interior side of the bottom sidewall 301 of the case bottom 300,contacts the end section 606 proximate to a first turn 608 of the wirespring 602. The first turn 608 is approximately 90°. A primary springsection 610 of the wire spring 602 is located proximate and parallel tothe interior side of the right sidewall 308 of the case bottom 300 andextends horizontally. A securing arm 372, connected to and extendingupward from the interior side of the bottom sidewall 301 of the casebottom 300, engages the primary spring section 610 proximate to thefirst turn 608. The attaching arm 370, right block 340, and securing arm372 of the case bottom 300 hold the wire spring 602 at positions justbefore, approximately at, and just after the first turn 608 of the wirespring (see also FIG. 6 for a view of these support structures).

A second turn 612 of the wire spring 602 is approximately 45°. Asecondary spring section 614 is horizontally oriented and extends in adirection approximately tangential to the circular opening 350 in thebottom sidewall 301 of the case bottom 300. A third turn 616 isapproximately 90°. A vertical section 618 of the wire spring 602 extendsvertically and terminates in a fourth turn 620, of approximately 90°.The wire spring 602 extends from the fourth turn 620 and forms an axlesection 622 which is horizontal and parallel to the secondary springsection 614. The axle section 622 extends through a central hole 624 inthe roller 604, which is thereby rotatably disposed on the axle sectionof the wire spring 602. The wire spring 602 is bent and positioned toresiliently bias the roller 604 against the ball 130.

As shown in FIGS. 6 and 7, axle supports 374 are connected to and extendupward from the interior side of the bottom sidewall 301 of the casebottom 300 adjacent to the sidewall 352 of the opening 350. The axlesupports 374 support portions of the axle section 622 of the wire spring602 on opposite sides of the roller 604. The axle section 622 of thewire spring 602 rests on upward facing horizontal surfaces 376 of theaxle supports 374. Vertical stops 378, extending upward from thehorizontal surfaces 376 of the axle supports 374, restrict outwardmovement of the axle section 622 of the wire spring 602 at oppositesides of the mounted roller 604. Vertical shields 380, extending upwardfrom the interior side of the bottom sidewall 301 of the case bottom300, form part of the sidewall 352 of the opening 350 and restrictinward movement of the axle section 622 of the wire spring 602 atopposite sides of the mounted roller 604. This allows a limited amountof horizontal radial movement of the axle section 622 and roller 604mounted thereon along the horizontal surfaces 376 of the axle supports374, thereby allowing flexing of the wire spring 602 for purposes ofcontinuously biasing the rotatable ball 130 against the encoder shafts510 (see FIG. 21) for coupling the ball to the transducers 110.

FIGS. 24 and 25 show the strain relief unit 700, which grasps the cord104 and transmits the mechanical strain experienced by the cord uponmovement of the mouse 100 to the housing 114 of the mouse and not to thecoupler 514 which connects the cord to the circuitry 512 on the printedcircuit board 500 (see FIG. 3). The strain relief unit 700 is preferablymade from flexible PVC, an elastomeric material. As shown in FIGS. 6 and7, an opening 382 in the front sidewall 322 of the case bottom 300receives the strain relief unit 700. Horizontal track supports 384,extending from the interior side of the front sidewall 322 of the casebottom 300 proximate to the opening 382, receive tabs 702 projectinghorizontally from the strain relief unit 700 (see FIG. 20) and restrainany rotation of the strain relief unit relative to the opening.

The strain relief unit 700 is shown in detail in FIGS. 24 and 25, andincludes a rear main plate 704, a reduced diameter intermediate section706 and a tapered forward plate 708. As shown in FIGS. 6 and 7, theopening 382 in the front sidewall 322 of the case bottom 300 includes agap 386. The case bottom 300 is constructed from flexible material, sothe gap 386 in the opening 382 allows the tapered forward plate 708 ofthe strain relief unit 700 to be pushed forward through the opening. Theintermediate section 706 expands and fits snugly within the opening 382.The rear main plate 704 and rearward facing side of the forward taperedplate 708 are each larger than the opening 382 in the front sidewall 322of the case bottom 300, so that, once in place, the strain relief unitcannot move backward or forward through the opening. The strain reliefunit 700 includes a covering tab 710 which, upon placement of the strainrelief unit in the opening 382, covers the gap 386. The strain reliefunit 700 is held in place solely by the case bottom 300 of the mouse100.

As shown in FIGS. 3 and 4, each of the encoder shafts 510 includes awheel pin 516 coaxially projecting from the end of the encoder shaftwhere the encoder wheel 506 is attached, and an end pin 518 coaxiallyprojecting from the end of the shaft away from the encoder wheels. Asshown in FIG. 6, a pair of wheel support arms 302 connect to and extendupward from the interior side of the bottom sidewall 301 of the casebottom 300, and have U-shaped free ends 362 which rotatably receive thewheel pins 516. A pair of shaft support arms 304 connect to and extendupward from the interior side of the bottom sidewall 301 of the casebottom 300, and have U-shaped free ends 362 which rotatably receive theend pins 518. One of each of the support arms 302 and 304 are spacedapart and positioned to support the encoder shaft 510 for one of theencoder wheels 506. The other one of each of the support arms 302 and304 are spaced apart and positioned to support the encoder shaft 510 forthe other of the encoder wheels 506.

The U-shaped free ends 362 of the support arms 302 and 304 support andhorizontally restrain the encoder shafts 510 and encoder wheels 506,while allowing the encoder wheels and shafts to freely rotate. Latcharms 366 are connected to and extend upward from the interior side ofthe bottom sidewall 301 of the case bottom 300, and flex to allowpositioning of the encoder shafts 510 and encoder wheels 506 in theU-shaped free ends 362 of the support arms 302 and 304. Upon positioningof the encoder wheels 506 and shafts 510, each of the latch arms 366extends over a middle portion of the corresponding one of the encodershafts 510, thereby restricting the upward movement of the shafts. Thisensures that each of the wheel pins 516 and end pins 518 cannot bedislodged from a corresponding one of the U-shaped free ends 362 of thesupport arms 302 and 304.

Although a specific embodiment of the present invention has beendescribed for purposes of illustration, various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, the invention is not limited by the disclosure, but insteadits scope is to be determined by reference to the following claims.

What is claimed is:
 1. An input device for providing user commands to acomputer comprising: a transducer for receiving user commands indicatingmovement of the input device and producing a position signal in responsethereto; a switch for receiving user commands indicating actuation ofsaid switch and producing a switch signal in response thereto; a controlcircuit coupled to said transducer and to said switch for receiving saidposition signal and said switch signal and providing an output signal tothe computer in response thereto; a case top forming a top side of ahousing, said transducer and said switch being positioned within saidhousing, said case top being of one-piece construction and including amain body and a first top securing member projecting from said main bodywithin said housing, said first top securing member including an armextending from an interior side of said main body and a tab extendingfrom a free end of said arm; and a case bottom forming a bottom side ofsaid housing, said case bottom being of one-piece construction andincluding a first sidewall and a first bottom securing member projectingfrom said first sidewall within said housing, said first bottom securingmember including a hook extending from an interior side of said firstsidewall, said hook releasably engaging said tab to releasably securesaid case bottom and said case top together.
 2. The input devicedescribed in claim 1: wherein said case top includes a second topsecuring member projecting from said main body within said housing, andwherein said case bottom includes a second bottom securing memberprojecting from a second sidewall within said housing, said secondbottom securing member releasably engaging said second top securingmember to releasably secure said case bottom and said case top together.3. The input device described in claim 2 wherein said first top securingmember and said first bottom securing member are each disposed toward aleft side within said housing, and wherein said second top securingmember and said second bottom securing member are each disposed toward aright side within said housing, and wherein said case top and said casebottom are fastened together by no more than a single selectivelyremovable fastener.
 4. The input device described in claim 3 whereinsaid selectively removable fastener is disposed toward a rear side ofsaid housing.
 5. An input device for providing user commands to acomputer comprising: a transducer for receiving user commands indicatingmovement of the input device and producing a position signal in responsethereto; a switch for receiving user commands indicating actuation ofsaid switch and producing a switch signal in response thereto; a controlcircuit coupled to said transducer and to said switch for receiving saidposition signal and said switch signal and providing an output signal tothe computer in response thereto; a case bottom forming a bottom side ofa housing, said transducer and said switch being positioned within saidhousing; a case top forming a top side of said housing, said case topincluding a main body and a button of unitary construction, said buttonbeing movable for user actuation of said switch; an arm extending froman interior side of said case top; and a hook extending from an interiorside of said case bottom, said hook releasably engaging said arm toreleasably secure said case bottom and said case top together, whereinsaid case top and said case bottom are held together by no more than asingle selectively removable fastener.
 6. An input device for providinguser commands to a computer comprising: a case bottom forming a bottomside of a housing; a case top forming a top side of said housing, saidcase top including first and second buttons which are independentlymovable between rest and actuation positions, and first and secondactuating members respectively projecting within said housing from saidfirst and second buttons; a transducer positioned within said housingfor receiving user commands indicating movement of said housing andproducing a position signal in response thereto; a control circuitcoupled to said transducer for receiving said position signal andproviding an output signal to the computer in response thereto; acircuit board positioned within said housing and having said controlcircuit mounted thereon, said control circuit including first and secondcontacts on said circuit board; and a switch package mounted on saidcircuit board, said switch package consisting of a switch case ofone-piece construction and a switch spring of one-piece construction,said switch spring being positioned within a recess of said switch case,said first and second actuating members of said case top respectivelycontacting and flexing said switch spring upon user actuation of saidfirst and second buttons to make first and second momentary electricalconnections between said switch spring and said first and secondcontacts on said circuit board, said first and second momentaryelectrical connections respectively producing first and second switchsignals, said control circuit receiving said first and second switchsignals and providing an output signal to the computer in responsethereto.
 7. The input device described in claim 6, wherein said switchcase includes a case securing member, and wherein said case bottomincludes a bottom securing member extending within said housing, saidbottom securing member releasably engaging said case securing member toremovably secure and position within said case bottom said switchpackage and said circuit board attached thereto.
 8. The input devicedescribed in claim 7, wherein said case top of said housing includes ahold-down member extending within said housing, said hold-down membercontacting said circuit board and restricting vertical movement of saidcircuit board.
 9. The input device described in claim 6 wherein saidswitch spring includes first and second contact leaves respectivelypositioned above said first and second contacts on said circuit board,said first and second actuating members of said case top respectivelycontacting and flexing said first and second contact leaves upon useractuation of said first and second buttons to make said first and secondmomentary electrical connections between said first and second contactleaves and said first and second contacts on said circuit board.
 10. Theinput device described in claim 9 wherein said switch spring includesfirst and second spring elements, said first and second spring elementsrespectively extending from said first and second contact leaves andbiasing said first and second contact leaves away from said first andsecond contacts on said circuit board.
 11. The input device described inclaim 10 wherein said switch case includes first and second supportmembers extending within said recess of said switch case, said first andsecond support members respectively supporting a free end of said firstand second spring elements, and wherein said switch case includes firstand second restraining members located within said recess of said switchcase, said first and second restraining members respectively restrainingupward travel of said first and second contact leaves resulting from anupward bias respectively imparted to said first and second contactleaves by said first and second spring elements.
 12. The input device ofclaim 9 wherein said first and second contact leaves of said switchspring are each fixed at one end to said switch case.
 13. An inputdevice for providing user commands to a computer comprising: a housinghaving a top side and a bottom side secured together; a rotatable ballreceived within said housing; first and second transducers positionedwithin said housing and coupled to said rotatable ball, said first andsecond transducers producing first and second signals indicative ofrotation of said ball; a switch positioned within said housing forreceiving user commands indicating actuation of said switch andproducing a switch signal in response thereto; a control circuit coupledto said first and second transducers and to said switch for receivingsaid first and second signals and said switch signal and providing anoutput signal to the computer in response thereto; and a retaining cagereceiving said ball and being constructed for removing from and securingto said bottom side of said housing with said ball therein, while saidbottom and top sides of said housing are secured together.
 14. The inputdevice described in claim 13 wherein said retaining cage includes anannular baseplate and a curved shield of unitary construction, saidcurved shield having an approximately spherical curvature and extendingfrom said annular base plate.
 15. The input device described in claim 14wherein said curved shield has an opening sized to allow said ball topass therethrough.
 16. The input device described in claim 14 whereinsaid curved shield includes a wing extending generally parallel to saidbaseplate and forming a gap therebetween, said gap receiving a shelfportion of said bottom side of said housing to removably secure saidretaining cage to said bottom side of said housing.
 17. An input devicefor providing user commands to a computer comprising: a housing formedfrom a case top and a case bottom; a transducer positioned within saidhousing for receiving user commands indicating movement of said housingand producing a position signal in response thereto; a switch positionedwithin said housing for receiving user commands indicating actuation ofsaid switch and producing a switch signal in response thereto; a controlcircuit coupled to said transducer and to said switch for receiving saidposition signal and said switch signal and providing an output signal tothe computer in response thereto; and a cord making a connection to saidcontrol circuit and carrying said output signal to the computer; and astrain relief unit grasping said cord and being mechanically fixedlyheld solely by said case bottom, said strain relief unit transmittingany mechanical strain experienced by said cord upon user movement of theinput device only to said case bottom.
 18. The input device described inclaim 17 wherein said strain relief unit includes a tapered portion, andsaid case bottom includes a flexible opening adapted to receive saidtapered portion therethrough to secure said strain relief unit to saidcase bottom.
 19. The input device described in claim 17 wherein saidstrain relief unit includes a projecting tab, and said case bottomincludes a track to receive said projecting tab to restrain rotation ofsaid strain relief unit relative to said case bottom.
 20. The inputdevice described in claim 17 wherein said strain relief unit includes aforward plate and a rear plate, and wherein said case bottom includes anopening, said forward plate positioned forward of said opening and saidrear plate positioned rearward of said opening when said strain reliefunit is held by said case bottom, said forward and rear plates sized torestrain forward and rearward motion of said strain relief unit relativeto said case bottom.
 21. The input device described in claim 20 whereinsaid forward plate is tapered and said opening is sufficiently flexibleto receive said forward plate therethrough to secure said strain reliefunit to said case bottom.
 22. An input device for providing usercommands to a computer, comprising: a housing having first and secondbuttons independently movable between rest and actuation positions;circuitry formed on a circuit board positioned within the housing, thecircuitry including first and second contacts on the circuit board; aswitch package consisting of a one-piece switch case and a one-pieceswitch spring, the switch spring positioned within the switch case, andthe switch case mounted on the circuit board, the switch spring beingoperable to make first and second electrical connections with the firstand second contacts, respectively, the first and second electricalconnections being independently produceable by the one-piece switchspring flexing in response to user actuation of the independentlymovable first and second buttons.
 23. The input device of claim 22wherein the housing includes a first securing member, and the switchcase includes a second securing member, the first securing memberengaging the second securing member to secure and position the switchpackage and the circuit board within the housing.
 24. The input deviceof claim 22 wherein each of the first and second buttons includes arespective one of first and second actuating members extending withinthe housing, the switch spring being engaged and flexed by the first andsecond actuating members in response to the user actuation of the firstand second buttons, respectively.
 25. The input device of claim 22wherein each of the first and second buttons includes a respective oneof first and second actuating members extending within the housing, andwherein the switch spring includes first and second contact leaves, thefirst and second actuating members operable to move the first and secondcontact leaves to make the first and second electrical connections withthe first and second contacts, all respectively.
 26. The input device ofclaim 22 wherein the switch spring includes first and second contactleaves respectively positioned near the first and second contacts, andwherein the switch spring includes first and second spring elementsrespectively biasing the first and second contact leaves away from thefirst and second contacts.
 27. The input device of claim 26 wherein theswitch case includes first and second support members, each supporting afree end of a respective one of the spring elements, and wherein theswitch case includes first and second restraining members, eachrestraining displacement of a respective one of the first and secondcontact leaves.
 28. The input device of claim 22 wherein the switchspring includes first and second contact leaves, each being fixed at oneend to the switch case.
 29. The input device of claim 22, furthercomprising a transducer positioned within the housing for receiving usercommands indicating movement.